Comparisons of Shear Stress/Shear Strain Relations of Wood Obtained By Iosipescu And Torsion Tests
Keywords:Shear stress/shear strain relation, Iosipescu test, torsion test
In this paper, we compared the shear stress/shear strain relations of wood obtained by Iosipescu and torsion tests.
Quartersawn boards of Sitka spruce (Picea sitchensis Carr.) and shioji (Japanese ash, Fraxinus spaethiana Lingelsh.) provided the specimens. Iosipescu tests were conducted with specimens loaded in the radial direction, and the shear stress/shear strain relations were obtained. Shear stress/shear strain relations were obtained independently of the Iosipescu tests by torsion tests of rectangular bars. The following results were obtained:
(1) The shear moduli, shear yield stresses, and shear strengths obtained from both methods showed good agreement with each other, except for the shear strength of ash.
(2) As for spruce, the difference between the shear stress/shear strain relations obtained by Iosipescu and torsion tests was significant in the 5% significance level, whereas that for the ash was not significant.
(3) Although the Iosipescu test can derive the shear stress/shear strain relation directly, it has the drawback that failure occurs earlier than with the torsion test. In contrast, the torsion test has the drawback that the procedure for obtaining the stress/strain relation is quite complicated. In determining the shear stress/shear strain relation of wood properly, shear stress/shear strain data should be measured more frequently by these methods.
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